Hearing aids with parts positioned deeply in an ear canal of a user, close to the user's eardrum, have a number of acoustical advantages compared to other types for instance with respect to suppression of feedback. Especially hearing aids with inflatable means provide a number of advantages also with respect to wearing comfort for the user.
U.S. Pat. No. 6,094,494 describes a device and method for fitting a sound transmission device to provide an easy and effective fit, reduce feedback, and improve user comfort comprises an ear-piece component having a face at one end with operative components and a stem adjacent the other end. The stem houses a speaker tube which protrudes from the component, and it has a retaining means for securing an inflatable, resilient fitting balloon thereon. The balloon has a sound transmission duct within it which can be coupled to the speaker tube so that when the balloon is secured to the stem, a continuous path is provided for the transmission of sound from the component to the user's ear canal external the balloon. This assembly (e.g., the component and attached balloon) is inserted into the ear canal when the balloon is in a deflated configuration. Air is then pumped into the balloon, e.g., through an air channel in the ear-piece component, to inflate the fitting balloon. The inflated fitting balloon engages the ear-piece component against the walls of the user's ear canal and prevents sound from travelling to the external ear and face of the component.
U.S. Pat. No. 4,133,984 describes a plug-type hearing device comprising a sound-leading portion being inserted into the auditory meatus, a first envelope attached around the sound-leading portion, a second envelope being positioned at the outside of the auditory meatus and being communicated with the first envelope through a pipe, and a holding means for holding an expanded state of the first envelope when the volume of the latter is increased, wherein the volume of the second envelope is decreased to increase the volume of the first envelope by the pressure of a fluid contained inside, and the expanded first envelope is closely contacted with the wall surface of the auditory meatus.
However, insertion of an object deeply into the ear canal, close to the eardrum, implies a high risk for occlusion of the sound transmission duct or sound port of the hearing aid due to cerumen being pressed into the sound duct opening or port during insertion. In case the duct or port is occluded this will result in malfunction of the hearing aid such as reduced efficiency and possibly also in a decreased lifetime of the hearing aid if delicate parts of the hearing aid are damaged due to cerumen. In addition, the described hearing aids are difficult to clean properly.